Model engine speed and power control mechanism



Feb. 20, 1968 H. A. JOHNSON 3,369,531

MODEL ENGINE SPEED AND POWER CONTROL MECHANISM Filed Feb. '7, 1966 FIG. I

INVENTOR E58 i. 5 l

HAROLD ALEC JOHNSON Patented Feb. 20, 1968 3,369,531 MODEL ENGINE SPEED AND POWER CONTROL MECHANISM Harold Alec Johnson, Los Angeles, Calif., assignor to American Machine and Foundry Company, a corporation of New Jersey Filed Feb. 7, 1966, Ser. No. 525,480 3 Claims. (Cl, 12365) ABSTRACT OF THE DISCLOSURE This invention relates to a model engine speed and power control arrangement comprising a cylindrical member mounted about the engine cylinder and having at least one aperture extending therethrough, said aperture being moved into and out of alignment with the exhaust ports in the engine by means of spring biasing control manner.

The present invention relates to miniature internal combustion engines such as are employed for operating small scale models of airplanes, boats, automobiles and similar toys, and more particularly to a simple but effective speed and power control mechanism for such engines.

In the familiar miniature model internal combustion engines of the two-cycle type, exhaust ports of fixed area are generally provided in the cylinder walls. These ports are uncovered during the downward stroke of the piston to permit exhausting to the atmosphere of the products of combustion and a consequent reduction of the pressure in the cylinder to the extent that a fresh charge of air-fuel mixture can enter the cylinder cavity. Internally positioned intake passage are generally uncovered soon after the opening of the exhaust ports to allow the entry of the new charge into the cylinder which assists in expelling the products of combustion, until the piston on its upward stroke closes the intake passages and exhaust ports in sequence, commencing a new power cycle.

In the usual engine of this type, the intake passages open at one end into the engine crankcase. Fuel for the engine is fed through a needle valve controlled orifice into the throat portion of a simple carburetor positioned adjacent the crankcase. The carburetor has an air inlet, and a valved outlet communicating with the crankcase. During the upward stroke of the piston, the valved outlet of the carburetor communicates with the crankcase, and air is caused to flow into the carburetor air inlet, past the orifice drawing fuel therefrom and comingling therewith, with the air-fuel mixture then flowing into the crankcase. During the downward stroke of the piston, the valved outlet of the carburetor is closed and the air-fuel mixture within the crankcase is compressed. Upon the opening of the intake passages, the compressed air-fuel mixture enters into the cylinder cavity as heretofore described. The construction and operation of such miniature two-cycle model engines are well known in the art, one such engine being fully described in US. Patent No. 2,838,035, entitled, Internal Combustion Engine, issued to Henry T. M. Rice on June 10, 1958.

Heretofore, control of the output power and corresponding engine speed of model two-cycle engines has often been accomplished by varying the amount of fuel entering the carburetor by varying the needle valve position. This control means permits only very limited power and speed variation, and moreover is too sensitive to permit random variation thereof from a remote point. Consequently, when used by hobbyists for operating a powered toy, the needle valve is initially adjusted to yield a desired power output and engine speed within a very limited range. After the powered toy is placed in operation no further control of the engine operation is possible and the toy continues to operate until the fuel supply is exhausted.

In other prior art arrangements, at butterfly valve is provided to regulate the fuel intake and a similar butterfly valve or a slide is provided on the exhaust to control the flow of exhaust gases from the engine. These designs while permitting remote control of the engine power and speed are more expensive to build and assemble than the present invention.

An object of the present invention is to provide a simple control mechanism for a model internal combustion engine which permits a variation of the engine speed and output power over a broad range.

Another object is to provide a new and improved control mechanism which varies the engine speed from an idle power value to a full power value.

Another object is to provide a neW and improved control mechanism which provides a large movement of the control lever over the range of engine speeds from idle or minimum power to full power output of the engine.

Another object is to provide such a control mechanism which can be readily operated from a point remote from the engine.

A further object is to provide such a control mechanism which can be automatically biased to a particular engine power output and speed.

Still a further object is to provide such a control mechanism which can be easily installed on the usual two-cycle model internal combustion engine.

Yet a further object is to provide such a control mechanism which is simple in construction and operation and is relatively inexpensive to manufacture.

Numerous other objects and advantages of the invention will be apparent as it is better understood from the following description, which, taken in connection with the accompanying drawings, discloses a preferred embodiment thereof.

Referring to the drawings:

FIGURE 1 is a side view of a two-cycle type model internal combustion engine having the speed and power control mechanism of the present invention with a portion of the control mechanism broken away;

FIGURE 2 is a sectional view taken substantially along the line 22 of FIGURE 1; and

FIGURE 3 is a perspective view of the sleeve portion of the control mechanism.

As a preferred or exemplary embodiment of the instant .invention, FIGS. 1 and 2 illustrate a model engine 10* of the two-cycle type particularly designed for use by hobbyists for powering scale model airplanes, automobiles, etc. The engine 10 has a cylinder 12 provided with external cooling fins and a glow plug 14 mounted in the cylinder head 16. The cylinder 12 is attached to a crankcase 18 which has a bearing support 20 rotatably mounting a crankshaft 22. The crankshaft 22 terminates in a crank arm (not shown) Within the crankcase 18, and has a crank pin connected to one end of a connecting rod in the usual manner (not shown) with the other end of the connecting rod being connected to a piston 24 which is reciprocable in the cylinder 12.

The cylinder 12 has a lower portion 26 with cylindrical inner and outer surfaces 28 and 30 respectively and with diametrically opposed exhaust openings or ports 32 extending between the inner and outer surfaces. In the embodiment illustrated, the exhaust ports 32 are formed by cutting slots in the lower portion 26 to produce circumferentially disposed openings of fixed area in the lower portion of the cylinder wall. The cylinder 12 also has a pair of diametrically opposed inlet passages 34 and 34 (as indicated by the dashed lines in FIG. 2), the inlet passages being disposed between the exhaust ports 32 and extending between the lower portion 26 of the cylinder and the interior of the crankcase 18.

The engine has a carburetor 36 with the carburetor housing 37 being formed integrally with the crankcase 18. The carburetor 36 has an air passage 38 opening at its outer end to the atmosphere. The inner end of the air passage 38 extends through the bearing support and is normally closed by the surface of a portion of the crankshaft 22 which is rotatably mounted in the bearing support. The crankshaft 22 is provided with an internal passage (not shown) having an opening 39 which is periodically aligned with the inner end of the carburetor air passage,38 and provides periodic communication between.

the carburetor air passage and the interior of the crankcase. The alignment of the opening 39 with the carburetor air passage 38 occurs during the upward stroke of the piston 24 so that air is drawn into the crankcase 18 due to the increasing volume below the piston.

A needlevalve 40 has a portion 42 disposed within the carburetor air passage 38 to form a carburetor throat of reduced flow area. The needle valve has a fuel inlet 44- adapted to be connected to a fuel supply (not shown) maintained at atmospheric pressure by suitable venting. An orifice 46 in the portion 42 is positioned substantially at the carburetor throat and permits fuel to be drawn from the fuel supply into the air passage 38 by the decreased pressure of the air as it flows at increased velocity past the throat of the carburetor. The rate of flow of the fuel, and thereby the output power and speed of the engine, is controlled by manual adjustment of the needle valve 40 by means of the adjusting screw 48.

The engine described is typical of the two-cycle model engines heretofore available for powering toy airplanes, automobiles, etc. In the operation of such powered toys, the engine is started and the needle valve 40 is then adjusted by manual manipulation of the adjusting screw 48 until the engine is operating smoothly and continuously, generally at its fastest speed as determined from its high pitched whine. No further adjustment of the needle valve 40 is subsequently made, and the toy is operated with the engine operating substantially at a constant power output and speed. To prevent inadvertent movement of the adjusting screw 48 due to vibration of the engine, a compression spring (not shown) is generally positioned on the shank of the screw between the head of the screw and the carburetor housing in the usualrnanner as will be familiar to those skilled in the art.

Powered toys of this type are often operated from a remote location using control lines or Wires attached to the toy by means of which the toy is constrained to move in a generally circular path. In some prior art devices, upon starting and initially adjusting the engine, the toy had to be manually restrained with the engine generally operating substantially at full power until the operator was ready to exert the proper control forces by means of the control lines. As soon as the toy was released it immediately and rapidly accelerated under the impetus of the full power output of the engine with consequent difiiculty in maintaining proper control over the toy. Moreover, the toy would continue to operate and require the operators attention and control until the fuel supply was exhausted, in which case the engine would cease to operate. In the case of a small scale model airplane type of toy, the unpowered airplane would tend to descend quite rapidly making it difiicult to control with an undesirably high probability of damage when it came into contact with the ground.

Whileit is possible in some prior art designs to control the engine power and speed from a remote control point, the present invention represents a distinct improvement over the prior art. The control mechanism of the present invention may be readily mounted on the engine without the complex assembly steps required by other designs. Furthermore, the subject invention is efficient, simple in construction and quite compatible with the engine design.

4 The control mechanism may also be marketed separately for home mounting by individuals.

In the preferred embodiment shown in FIG. 1-3, the engine 10 is provided with a control mechanism generally designated 50 which includes a circular sleeve 52 having a cylindrical inner surface 54, circumferentially disposed cooling fins 56 on the outer surface of the sleeve, diametrically opposed cut-outs or slots 58, and an aperture 60 adjacent one of the slots 58 and positioned in a groove 62 formed by two adjacent cooling fins 56. As previously described, the lower. portion 26 of the cylinder 12 which includes the exhaust ports 32 has. a cylindrical outer surface. The sleeve 52 is rotatably mounted on the lower cylinder portion26 with the surface 54 of the sleeve adjacent to the surface 30.

A formed wire control member 64 has an arcuate portion 66 disposed in the groove 62, a hooked end 68 extending radially inwardly through the aperture 60 beyond the inner surface 54 of the sleeve 52, and a lever portion 70 terminating in a eyelet 72 disposed outwardly of the cooling fins 56. An extensible spring 74 having one end attached to the lever portion 70 of the control member 64 and the other end attached to the carburetor housing 37 rotationally biases the sleeve 52 in a counter-clockwise:

direction as viewed in FIG. 2 to a limiting position wherein the inwardly extending hooked ,end 68 of the control member abuts a surface 76 of the exhaust port 32;

In this limiting position, the slots 58 are disposed over the surface 30 of the lower cylinder portion 26 and out of alignment withthe exhaust ports 32. The exhaust ports 32 are thereby fully throttled by the sleeve 52, and the escape of thehighly pressurized products of combustion from the cylinder 12 is restricted to the annular flow path formed between the adjacent surfaces 30 and 54 of the cylinder lower portion 26 and sleeve 52 respectively. For this purpose, a predetermined clearance is provided between the surfaces 30 and 54. The cooling fins 56 dissipate,

the heat transferred to the sleeve 52 from the hot exhaust gases and prevent overheating of the control mechanism.

The throttling of the exhaust ports32 in the manner indicated results in incomplete exhaustionof the products of combustion and a consequent increased residual pressure of the unexhausted gases in the cylinder to the extent that the quantity of the air-fuel mixture entering the cylinder during each inake cycle is reduced, which correspondingly reduces the power output and speed of the englne. The clearance provided between the surfaces 30 and 54 is selected so as to restrict the exhaust area with the sleeve 52 .in the limiting position to the point re-.

quired for minimum engine speed without causing the engine to stall, corresponding to idling of the engine. With.

a model engine of the type described, a clearance of .O01-.O02 inch has been found to provide satisfactory idling operation at minimum speed and power.

As the sleeve 52 is rotated in a clockwise direction as viewed in FIG. 2, increasing areas of the exhaust ports 32 are exposed to the atmosphere through the slots 58, and the throttling of the exhaust portsis progessively reduced. The escape of the exhaust gases is thereby facilitated, and a progressively increasing quantity of the air-fuel mixture enters the cylinder during each intake cycle with a resultant progressive increase in engine power output and speed. When the sleeve 52 has been rotated to a position wherein the slots 58 are fully aligned with the exhaust ports 32, the throttling of the exhaust ports is at a minimum value and the escape of the exhaust gases occurs at the most rapid rate. The substantially complete dissipation of the exhaust gases from the cylinder permits a maximum quantity of the air-fuel mixture to enter the cylinder during each intake cycle, and the operation of the engine is at maximum power and speed.

The control mechanism described permits a full range of variation from minimum to maximum engine power and speed to be attained by controlling the alignment of the slots 58 and exhaust ports 32. Instant or gradual acceleration and deceleration can be had by varying the speed with which the sleeve is rotated. Since the control mechanism 50 is a separate part mounted exteriorly of the engine 10, the control mechanism can be readily installed on many of the available miniature two-cycle engines used by hobbyists without modifying the engine in any material respect.

The control mechanism of the present invention is particularly suited for operation from a remote point, as, for example, controlling the operation of powered scale model airplanes or automobiles operated from a remote point using control lines. In such instances, an additional control wire connected to the eyelet 72 of the control member can be provided to manipulate the position of the sleeve 52 to vary the engine output and speed as desired for starting, stopping, take 01f, landing, maneuvering, etc. Moreover, the relatively large arc of travel of the eyelet '72 required to vary the position of the sleeve 52 from minimum or idle power and speed to maximum or full power and speed is a desirable feature in that the control mechanism is not overly sensitive to the position of the eyelet and little skill is required to satisfactorily manipulate the throttle control wire. A child can therefore readily acquire the degree or" skill required to properly control a powered airplane or similar toy.

In the preferred embodiment described, upon release of the throttle control wire the spring 74 immediately returns the sleeve 52 to the limiting position fully throttling the exhaust ports 32, whereupon the engine operates at minimum power and speed. It is to be understood of course that depending upon the manner in which the engine is being used as a power source, the control mechanism may be biased to a higher engine power and speed, including full power, or alternatively there may be no provision for biasin the control mechanism to any particular power and speed.

It is thought that the invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various dhanges may be made in the form, construction, and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred embodiment thereof,

I claim:

1. A control device for a two-cycle internal combustion engine having a cylinder, a piston reciprocable in said cylinder, and at least one exhaust port in said cylinder whereby the products of combustion are exhausted from said cylinder, said control device comprising:

a cylindrical member having an opening extending axially therethrough adapted to be rotatably mounted about the engine cylinder and a plurality of spaced outwardly extending cooling fins formed on the outer surface thereof and including an aperture adjacent each cylinder exhaust port designed to be moved into positions wherein varying areas of said aperture are aligned with said exhaust ports to variably throttle the exhaust ports,

control means mounted at one end to said cylindrical member and including a body portion extending thereabout with the other end of said control means extending outwardly therefrom for coupling to a control line whereby the apertures are moved into varying degrees of alignment with said exhaust ports to control the engine speed,

spring means mounted at one end to the engine and at the other end to the outwardly extending end of the control means to limit the rotational movement of the cylindrical member relative to the engine cylinder and wherein the cylindrical member includes an aperture extending through the wall thereof between two adjacent fins, and

the control means comprises a formed wire control member having an arcuate portion disposed in the groove formed of two outwardly extending adjacent fins, a hooked end extending radially inward to be mounted through the aperture in the cylindrical member and beyond the inner surface thereof and a lower portion disposed outwardly of the cooling fins on the cylindrical member.

2. A control device in accordance with claim 1 wherein:

the spring means comprises an extensible spring having one end mounted to the lever portion of the control member and the other end mounted to the engine to rotationally bias the cylindrical member in a predetermined direction to a limiting position wherein the inwardly extending hooked end of the control member abuts a surface of the exhaust port to fully throttle said engine.

3. A control device in accordance with claim 2 wherein:

the cylindrical member includes a surface concentrically disposed with respect to the engine cylinder with a predetermined spacing therebetween to permit the exhaust gases to escape when the exhaust ports are closed and thereby prevent engine stalling.

References Cited UNITED STATES PATENTS 2,921,568 1/1960 Mettetal 123107 2,940,434 6/ 1960 Stanzel 123107 FOREIGN PATENTS 2,446 8/ 1918 Netherlands. 61,224 7/ 1938 Norway.

WENDELL E. BURNS, Primary Examiner,

MARK M, NEWMAN, Examiner. 

